Ceramic dielectric



March 1969 SHIGEKAZU HAYASHl ET AL 3,431,124

I CERAMIC DIELECTRIC Filed June 10, 1964 Sheet of 3 F/g. A

9O 80 TO 60 5O 4O 3O 20 IO Lo203-2TiO2 w WOO A L02 03,2Ti02 Mamh 1969SHIGEKAZU HAYASHI ETAL 3,431,124

7 CERAMIC DIELECTRIC Filed June 10. 1964 Sheet 3 of 5 9O 8O 7O 6O 5O 4O3O 20 IO 9O 8O 7O 6O 5O 4O 3O 20 IO March 4, 1969 SH|GEKAZU HAYASH1 ETAL 3,431,124

- CERAMIC DIELECTRIC Filed June 10, 1964 Sheet 5 V 90 8O 7O 6O 5O 4O 3O20 IO United States Patent 2 Claims ABSTRACT OF THE DISCLOSURE Adielectric having a high dielectric constant, a low temperaturecoefiicient and loss coefl'icient, a high stability and a lowdeterioration rate consisting of a ceramic composed of 2 to 97 molpercent of CaTiO 3 to 40 mol percent or La O -2TiO and 0 to 95 molpercent of MgTiO;.;.

It is generally desirable that a ceramic dielectric should have a highdielectric constant, a low temperature coefiicient and loss coefiicient,a high stability and little deterioration with the lapse of years.

The dielectrics of comparatively favourable characteristics that hasbeen conventionally used in practice are composed mostly of titaniumoxide TiO calcium titanate CaTiO or magnesium titanate MgTiO Thedielectric constant of the dielectric composed mostly of TiO or CaTiO is100 to 150. That of the one composed mostly of MgTiO;, is 15 to 45. Thecomposition CaTiO -MgTiO has been known, but this has been able to giveonly characteristics which lie within the above mentioned range. Thussuch dielectrics have respectively dilferent ranges of dielectricconstants. Therefore, it has been impossible to produce of the samesystem material a dielectric having a dielectric constant in a widerange. Thus the production process has been complicated and has resultedin a high cost. Further, in the conventional dielectric, no desireddielectric constant high enough can be obtained and therefore it isalmost impossible to make the parts of electronic instrument smaller forthe remarkable development of the electronic industry. The presentinvention has been suggested to eliminate the said defect.

A principal object of the present invention is to provide new ceramicdielectrics which have wide ranges of dielectric constants, can be madeof the same system materials and are higher in dielectric constant andlower in loss coeificient than any conventional dielectrics.

Another object of the present invention is to provide new ceramicdielectrics which may have temperature coeflicients in wide ranges, arehigh in dielectric constant and have very high Q-values.

FIGURE 1A is a ternary diagram of the dielectric compositions of thepresent invention.

FIGURE 1B shows the characteristics of the same dielectrics, that is tosay, in FIGURE 1B, the values of the dielectric constants, Q andtemperature coefficients of the respective points in FIGURE 1A arearranged in turn from above.

FIGURE 2 shows the dielectric constant of the product of the presentinvention.

FIGURE 3 shows the values of Q of the same.

FIGURE 4 shows the temperature coefiicients of the same dielectrics.

The present invention relates to a ceramic dielectric product of thematerials composed of 2 to 97 mol percent CaTiO' 3 to 40 mol percent LaO -2TiO and 0 to 95 mol percent MgTiO The dielectric of the presentinvention has a dielectric constant of 15 to 180 and a Q-value of 5,000to 20,000. As compared, for example, with the Patented Mar. 4, 1969dielectric constant of 15 to 45 and the Q-value of 4,000 to 5,000 of aconventional dielectric composed mostly of MgTiO the product of thepresent invention is found to be superior.

The most suitable composition to obtain the expected characteristics inthe dielectric of the present invention is 2 to 97 mol percent CaTi0 3to 40 mol percent La O -2TiO and 0 to 95 mol percent MgTiO in the rangeenclosed within the framework in FIGURE 1A, because, in case CaTiO isless than 2 mol percent and MgTiO is more than 95 mol percent, the valueof the dielectric constant will be less than 15. When CaTiO is more than97 mol percent the ceramic sintering temperature will be so high as tobe above 1,400 C. and, further when La O -2TiO is more than 40 molpercent, the value of Q will be less than 2,000 and, when it is lessthan 3 mol percent, the effect of the improvement showing the excellentfeatures of the high dielectric constant and the low loss by theaddition of LaTiO -2TiO will not be seen.

Examples of the present invention shall be described in the following.

Example 1 Titanium-dioxide TiO calcium carbonate CaCO and lanthanumoxide La O were mixed together so as to be the composition 1 in FIGURE1A i.e. a composition of mol percent CaTiO and 15 mol percent La O -2TiOThe mixture was calcined at 1,230 C. for hours in an oxygen-containingatmosphere, was crushed to be a fine powder, was then moulded and wasfired again. The dielectric produced by said process showed a dielectricconstant of 140 and a Q-value of 7,000. The producing conditions in thefollowing examples were the same as in this example.

Example 2 A ceramic dielectric produced by mixing the raw materials soas to be the composition 2 in FIGURE 1A i.e. a composition of 60 molpercent CaTiO 15 mol percent La O -2TiO and 25 mol percent MgTiO had adielectric constant of 70 and a Q-value of 10,000.

Example 3 A ceramic dielectric produced by mixing the raw materials soas to be the composition 3 in FIGURE 1A i.e. a composition of 30 molpercent CaTiO 20 mol percent La O -2TiO and 50 mol percent MgTiO had adielectric constant of 18 and a Q-value of 15,000.

Example 4 A ceramic dielectric produced by mixing the raw materials soas to be the composition 4 in FIGURE 1A i.e. a composition of 10 molpercent CaTiO 10 mol percent La O -2TiO and 80 mol percent MgTiO had adielectric constant of 15 and a Q-value of 17,000.

Example 5 A ceramic dielectric produced by mixing the raw materials soas to be the composition 5 in FIGURE 1A i.e. a composition of molpercent CaTiO and 5 mol percent La O -2TiO had a dielectric constant of180 and a Q-value of 7,000.

As in the above, ceramic dielectric consisting of 2 to 97 mol percentCaTiO 3 to 40 mol percent La O -2TiO and 0 to 95 mol percent MgTiO havedielectric constants in the range as 15 to 180 which is wider than thatof any conventional dielectric and a very high Q-value.

Further if the compositions are selected so as to be in the ranges of 45to 97 mol percent CaTiO 3 to 40 mol percent La O -2TiO and 0 to 40 molpercent MgTiO the dielectric constant and temperature coefficient can bemade to be in the ranges 34 to 170 and +100 to Example 6 A capacitorproduced by mixing the raw materials so as to be a composition of 60 molpercent CaTiO 30 mol percent La O '2TiO and 10 mol percent MgTiO showede of 80, Q of 6,500 and a temperature coefficient of -230 10 C.

Example 7 A capacitor produced by mixing the raw materials so as to be acomposition of 90 mol percent CaTiO 8 mol percent La O -2TiO and 2 molpercent MgTiO had values of e of 145, Q of 5,000 and a temperaturecoefficient of 750X l C.

Example 8 A capacitor produced by mixing the raw materials so as to be acomposition of 46 mol percent CaTiO 39 mol percent La O -2TiO and 16 molpercent MgTiO had values of 6:30, Q=5,500 and a temperaturecoefficient=+100 10 C.

As is evident from the said examples, the ceramic dielectric accordingto the present invention have a dielectric constant in the range 15 to180 which is wider than of any conventional one and in addition to veryhigh eand Q-values, its temperature coefiicient can be selected in awider range. Therefore, according to the present invention, the trend tosmaller products can be accelerated and dielectrics which are cheap asparts of radio, television and various communication instruments and hasvery excellent characteristics can be obtained.

What is claimed is:

1. A ceramic dielectric consisting essentially of 2 to 97 mol percentCaTiO 3 to mol percent La O -2TiO and 0 to 95 mol percent MgTiO;,.

2. The ceramic dielectric defined in claim 1, wherein the content ofCaTiO amounts to from to 97 mol percent and the content of MgTiO;; is 0to 40 mol percent.

References Cited UNITED STATES PATENTS 2,689,185 9/1954 Soyck l06392,741,561 4/1956 Das Gupta 106-46 2,985,700 5/1961 Johnston 106-393,268,783 8/1966 Saburi 317258 FOREIGN PATENTS 574,577 1/ 1946 GreatBritain.

OTHER REFERENCES Marzullo et al.: Dielectric Properties of Titania orTin Oxide Containing Varying Proportions of Rare-Earth Oxides, J. Am.Cer. Soc., vol. 41, January 1958, pp. 40-41.

Mac Chesney et al.: The System La O TiO Phase Equilibria and ElectricalProperties, vol. 45, September 1962, pp. 416-42.

HELEN M. McCARTHY, Primary Examiner.

